Brush Spring Layout for Constant-Pressure Electric Motors
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Solution Overview
Problem
Existing brushed electric motors face a significant issue with coil or torsion springs, where the pressure difference between initial and final stages of brush wear leads to increased friction and reduced efficiency and lifespan due to non-uniform load application on the brush.
Innovation Solution
The electric motor design incorporates a brush spring with a first and second spiral portion made of a strip-shaped material, coupled by a coupling portion that applies a uniform load to the brush, ensuring consistent contact with the commutator without requiring the brush to be shortened.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a coil spring or torsion spring is used as the brush spring, then the brush can be pressed against the commutator, but the pressure difference between initial and final stages of brush wear increases, leading to increased friction and reduced efficiency
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional coil or torsion springs to a constant load spring that maintains uniform pressure characteristics. The constant load spring is designed with specific geometric parameters (spiral shape, wire diameter, mean coil diameter) to achieve constant load application, fundamentally changing the pressure parameter behavior from variable to constant throughout brush wear.
Solution Approach 2:
The invention implements dynamics by designing the brush spring system to adapt to brush wear. The constant load spring dynamically maintains constant pressure on the brush despite changes in brush length during wear, ensuring uniform load application throughout the brush lifespan and preventing excessive friction and energy loss.
2Stability of the object's composition
If a constant load spring with spiral portion is used to apply uniform load to the brush, then the pressure uniformity improves, but the brush length must be shortened by at least the dimension of the spiral portion
Solution Approach 1:
The patent resolves the spatial conflict by repositioning the spiral portion from a longitudinal arrangement (behind the brush) to a transverse arrangement (at the rear end surface). This dimensional change allows the spiral portion to be positioned perpendicular to the brush length direction, eliminating the need to shorten the brush while still achieving constant load application.
Solution Approach 2:
Instead of placing the spiral portion behind the brush in the conventional manner, the invention inverts the arrangement by positioning the spiral portion at the rear end surface of the brush, with the coupling portion extending backward. This inverted configuration allows the constant load spring to function without requiring brush shortening.
3Reliability
If the initial pressure is set high to secure predetermined final pressure, then the final pressure requirement is met, but the friction between brush and commutator increases during rotation
Solution Approach 1:
The constant load spring is designed to be self-regulating, automatically maintaining constant pressure on the brush throughout its wear lifecycle. The spring's geometric design (spiral configuration with specific parameters) enables it to self-adjust and deliver uniform load without external intervention, ensuring both reliability and low friction operation.
Solution Approach 2:
The invention changes the pressure parameter from variable (high initial, low final) to constant throughout brush wear. By carefully selecting the spring parameters (wire diameter, mean coil diameter, number of coils), the system achieves predetermined final pressure while maintaining uniform pressure, thereby preventing excessive friction and heat generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design maintains brush length throughout its lifespan, thereby enhancing motor efficiency and extending the overall lifespan of the electric motor.
Implementation Method 1
The constant load spring is a spiral spring having a spiral portion in which a wire material having a strip shape is spirally wound. The constant load spring is arranged such that the spiral portion comes into contact with a rear end surface of the brush. As a result, the constant load can be applied to the rear end surface of the brush by the spiral portion by using a force by which the spiral portion returns to an original state when the strip-shaped wire material is stretched from the spiral portion.
Data Source
AI summary
An electric motor includes a rotor including a rotating shaft extending in an axial direction, a commutator that is attached to the rotating shaft, a brush that comes into contact with the commutator, and a brush spring that presses the brush against the commutator. The brush spring includes a first spiral portion and a second spiral portion, each of the first spiral portion and the second spiral portion being made of a plate material having a strip shape wound in a spiral shape, and a coupling portion that couples a wire material having a strip shape forming the first spiral portion and a wire material having a strip shape forming the second spiral portion, and the brush is pressed against the commutator by a load from the coupling portion.